We could be using an app-centric XML-like language¹ for the UI, and an app-centric protocol versus a stateless² one where we apply hacks like cookies and WebSockets to. Instead we're hacking on top of a document-oriented system, and the hacks feel like they're 10 layers deep now.
¹ Similar to XAML or XUL, in concept and example.
² Statelessness is a great default, but when you need it, it shouldn't be an awful hack.
All of those things are significantly different than a mainframe/term setup
It's not actually true (unicode alone is a big improvement), but even if it was, so what? If a technology already fulfilled those needs pretty well, why would you expect major improvements to arise? The improvements come from the fact that you don't have to restrict yourself to text and labels.
Maybe not, but you certainly shouldn't expect a regression, which is exactly what we're witnessing.
And there's a fair bit of truth to that.
You can: just write a C# or whatever app, and use some stateful protocol.
In any case, I find the whole "layers deep" to be a major overstatement. WebSockets are essentially framed TCP sockets, with a single initial handshake that looks like HTTP. They are not a "layer" over HTTP or anything like that.